Actually, you're wrong

I know comparing alcohol, cannabis, and tobacco is like comparing three competly different things from deep space but they are the most commonly used substances in the western world

Caffeine and sugar are certainly more used than cannabis and tobacco; and at least sugar is more used than alcohol.

And this points to the real issue. Every drug taboo or lack of it is cultural - for instance, caffeine is more dangerous than cannabis; combined with certain diseases it might be as dangerous as tobacco; sugar is likely more dangerous than all of the above, cumulatively (if not acutely); and then, not all alcohol is equally dangerous: the active chemical is the same, but beer and wine are sure not in the league of distilled spirits in regards to dangers, both acute and chronic. Now, as all culturally dependant taboos, it runs afoul of church-state separation (remember how the adventists don't do caffeine, the Mormons don't do tobacco, the Muslims don't do alcohol??). Therefore, I am against all drug bans. ALL drug bans.

And if Rule # 6 didn't prevent me, I'd detail my answer.

In any case, "all" drug bans includes alike universal drug bans and age-based bans. So yes, age laws for this should also be abolished.

And no, it doesn't have to do with responsibility, because free societies choose to allow the responsible the exercise of freedoms even if the irresponsible will misuse them, not vice versa.